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620KC on 720 bare frame build


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1 hour ago, datsunfreak said:


That hits a little too close to home for me...  😄

Hahaha me too. 


"I already have to build custom doors, how hard can suicide doors be beyond that?"  - A massive idiot (aka me).

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  • 2 weeks later...

Haven't been spending enough time in the shop lately as work has been hectic plus we've been suffering under a heat wave (cloudless skies combined with daily temps near 100F, and 17 hours of daylight for that heat to soak in)


 Enough bitchin...


Have the Left side inner fender/cowl ready for finish welding then can repeat for the Right side.






As I had previously fit the doors up, doing the repairs to the bottom edges will be next and then I can say that all the major body repairs (cab only, haven't started on the box yet) will be done. I'll still have several small repairs to do - most on the front rad support - and I can finally mount the cab to the frame and change my focus back to mechanicals like getting the engine plumbed and wired up.

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  • 1 month later...

Work on the project has been continuing though at a reduced pace thanks to work being quite busy lately. Time or money - never the 2 in abundance together!


My iPhone has decided lately that it won't send my photos to my email so no pics until I get that sorted out. I have been working on resolving the problem about my door releases being now too far forward thanks to the dash swap, and at the same time I'm working on the rusted-out door bottoms. I have worked on the fit & alignment of the replacement front fenders - both being aftermarket - and with the body lines now matching up I will have the ability to make sure the door body lines look proper.


Have I mentioned that I hate doing bodywork?

Still have a good number of small rust-throughs around the rad support/headlight bucket areas to deal with, primarily cosmetic and ultimately hidden so I won't be spending too much time on those. I really want to get the cab back onto the frame so I can start with the electrical and plumbing connections

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Picking away on the fit of the fenders, the leading end of my hand built rockers didn't quite fit the fenders properly so I now have to rectify this (on both sides) before I go further. Gimme a bigger hammer dammmit!


I massaged the non-OEM right fender and it now otherwise fits pretty good, the left didn't need much since it had previously been part of a 620.


The left side door release has been moved 2" rearward and should operate normally, as long as there are not issues with the window moving up/down.



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  • 1 month later...

The main area of issue was the lip that is supposed to lay up against the area where the hinges are, the profile didn't match very well but was massaged to fit.


I've been squeezing in what little time has been available and have got the cab pretty near ready to put onto the frame and begin sorting the cooling/electrical/steering bits. A quick look at the heater assemblies show some significant differences between the 620 & 720 units, suspect there's gonna be some bastardization involved as the plan is to use the 720 system (more CFM, future potential of AC, etc.) PLUS the 720 steering column doesn't look like it'll line up to the 620 mounts & firewall. My intent is to try to get things to look more factory than rat rod.


Anyway, the cab rust patches are complete and cab is fully undercoated, and engine bay is primed. Hope to have the cab mounted up this weekend or by next if I have time.






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  • 2 weeks later...

Cab is installed for another test fit, identifying 4 points of minor contact that will be addressed shortly today - 2 on upper control arms & 2 on power steering box.


Have sorted out the wiper motor fitment as the 720 mounted in the engine bay vs the 620 mounting behind the dash. New mount plate made and wiper arm modified. Why not just use the original motor? Well the 720 wiring harness & motor have different connection as the 720 featured intermittent wipe, not an option on the 620. I might was well have everything work!


Next up is to fit the 720 steering column, noting the mounting plate is very different between the 2 generations, with the 720 mount having a bend and looking like it went through the firewall a bit lower than the 620 did. This is my opportunity to make the alignment and position fit relative to the dash, the seat, and most importantly me. Comfort for long haul cruising!

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The door pull handles I just shortened them. I don't remember mine being so far forward as yours. All I did was take the bent end off and they were fine. Filed the end round and smooth... not like anyone can see them. Is your dash fully forward against the window?


I relocated the wiper inside the plenum and sealed the hole. Had to clock the wiper arm and weld it but worked perfectly.

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  • 2 weeks later...

Been busy working on the truck as free time permits, and seeing Noll's Z progess has prompted me some!

After a few minor body contact spots resolved, the cab is on the final fit up and progress continues.


The 720 steering column is fully installed and larger brake booster from the 720 is in, requiring mods to the standoff for clutch master clearance, plus some recontouring of the inner fender for clearance.

IMG_7858.thumb.jpg.a198e365fa1b4ee49d33682125d0f6d1.jpg IMG_7859.thumb.jpg.8d45a3a5450a9f433924207e45d93e97.jpg IMG_7861.thumb.jpg.87da912938cfbf2b0db96e292f41451e.jpg IMG_7871.thumb.jpg.6c8ff314b8bca209397c9483b8913e75.jpg


The rad is test fit for mounting brackets, and have definate need for a pusher fan. Will see if I can reverse mount the fan blades so the unit I have is efficient when I wire the fan reversed - fan blades are scooped to pull air.



Next up is the hardlines for brakes n clutch.


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  • 4 weeks later...

Radiator fan has been successfully converted to pusher and has very little run-out, so I'm calling that good. All mounted up now onto the rad.

IMG_7924b.thumb.jpg.671876ba3531a8a081a0950ac853de2b.jpg IMG_8002.thumb.jpg.d0ed4ce4c9da40f112fb6e1f108f2ffe.jpg

After lots of time spent doing CAD work, I have fabricated lower supports plus side and top shrouds and I'm liking how that has turned out. Everything has rubber isolation so there shouldn't be any noises from this.

IMG_7983.thumb.jpg.11dc53202e3a99ee8ed80c1fc22095a7.jpg IMG_7998.thumb.jpg.6e41892d7e47880a5ca880f7d5c8fc60.jpg

There is a fairly large space below the rad as the new rad is far more rectangular, so I have devised a means to fill in that which will double to direct airflow through the rad.



I'm happy with how this is working out and can shift my focus onto other tasks.

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2 hours ago, Stoffregen Motorsports said:

Is the plate at the firewall welded to the column?

Hmmmmn, I hadn't thought about that. The plate is a 2 piece so I can tack it up, pull the assembly out & weld it up.

Thanks for that heads up.

2 hours ago, Stoffregen Motorsports said:

Nice clean work.

Thanks, while this won't be a show car by any stretch I do try to make things neat & tidy. Too bad my own body welding isn't up to my standards!

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I appreciate the creativity that can be found in true Rat Rods, but at times I find the workmanship in some builds to be truly sketchy and I've seen things that are unsafe, possibly illegal but certainly wouldn't pass inspection anywhere. I was taught long ago that there are 2 areas you NEVER weld on or modify - steering and brake components, but I've seen leaf springs welded to frames, brake flex lines that are rubbing on suspension components, & other shit that screams "Death soon to whoever rides in this".


Not for this cranky old bastard!

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There is one specific build thread here on this forum that scares the shit out of me. I won't call the guy out by name, but it's in the 521 section. Complete hack job, for the sake of hacking. Totally ill conceived and poorly executed to the point of being dangerous.

Edited by Stoffregen Motorsports
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I hear you on that. I don't know the build you refer to and probably don't really need to know either, I won't be going to drive it or hopefully be on the road anywhere near it. Is it just a lack of skill, planning & execution, or intentional hack? Many people learn by doing & without someone knowlegable to guide them, well... I was lucky growing up that my neighbor was into cars as my dad wasn't and didn't have the skills either.



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  • 2 weeks later...

Area below radiator is now filled in and just needing to do a bit of trimming to get the fit how I want, and add some anchors to the bottom edge to keep it all in place.

IMG_8043.thumb.jpg.3caa55b5b135b1dbf0eda4c711c591e7.jpg IMG_8044.thumb.jpg.b3a5d2e8f5fb3b52461568aba994c715.jpg


Have to give up 1/2 my garage space now to fit the wife's car inside for the next few winter months, so some tasks will be juggled due to the new workspace limitations.


Big task ahead of me is to figure out my heater unit as there is a world of difference between the 620 and 720 units. I'll post pics soon of just how different these uits are.


Mike, you had swapped a 720 dash into a 620 before, how did you accomplish this?

  • Like 3
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On 12/2/2021 at 11:06 AM, Z23T said:

Nice aluminum work on the radiator mounts.

Thanks, I used stainless steel as I happened across a suitably sized panel from my local metal shop that already had one of the bends I'd needed anyway. Fate!

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Well it appears that I have my work cut out for me. I knew there was going to be a significant difference between the 2 series heater assemblies, just not THIS MUCH!

Somehow I need to fit not just the core from the 720, but the blower is a separate unit that is connected by a bridge duct. As you can see, the overall width is significant.


Not to mention the air intake is in a different place, noting the 620 has fresh air vents at each end of the dash. This is possibly the hardest part of the build to sort out. The ducts themselves won't be hard to figure and I can scavenge that shit from a wreckers.


The mounts to the cab can be figured out too:


IMG_8059b.thumb.jpg.dcad03b44f6c6f94f65faaa17c1875d1.jpg IMG_8061b.thumb.jpg.51c0cf61f2ddcd5cc63c65e360ca0b73.jpg


IMG_8063b.thumb.jpg.ff32e9ad9009be1cf53dd0f37666eeed.jpg IMG_8065b.thumb.jpg.8ab0bd6c0dd0957f9e3b8bb6ae911991.jpg

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Further to my big challenge in adapting the 720 HVAC into the 620, the 620 HVAC is a far, far simpler system having just 2 ducts to the defroster, and the bottom flap just opens to dump heat onto the floor. The fan motor is smaller & has 2 speeds (Hi/Low). The 620 dash has no heat to the outboard ends, only the direct fresh air vents. Pretty compact.


The 720 has more ducting alone than the amount of space the 620 HVAC takes up.

249054624_720ducts.jpg.94ff4892d7f554e8b674f6aa4c70734f.jpg IMG_8100.thumb.jpg.e38a1d38646f9b4275567911b565a2c8.jpg

I'm really seriously rethinking the 720 dash/HVAC as a result. The fan is definitely bigger & moves more air, plus has 4 speeds. There's just SO MUCH STUFF. Thank god I still have the 620 dash.


So I have jumped on refurbishing the 620 system, and will find a way to get more fan speed, possibly make some ductwork to move air to the end vents. If you recall, that heater came with a mouse home complete with former resident so needed a freshening anyway. Worst case, I'll have a fully refurbed unit to sell... Or one for a 720 complete...



Driving to Whitehorse tomorrow so project gonna sit for the rest of the week & I'll ponder my next move.

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